Cellulose digester



v Oct. 27, 1936. F w. l.. scHlLDE 2,059,149

cELLULosE DIGESTER Filed NOV. 4, 1935 7 M. Sc/n'lcle i Patented Oct. 27, 1936 UNITED STATES CELLULO SE DIGESTER Friedrich Wilhelm Ludwig Schilde, Graz, Austria Application November 4, 1935, Serial No. 48,241

' In Austria November 10, 41934 4 Claims.

This invention relates to cellulose digesters.

As is well known in the art, these digesters are provided with special means or devices for evacuating the digester before commencement of the 5 boiling (provided such evacuating be contemplated), as also for introducing the lye, for turning over the liquor in the digester (when necessitated by close packing of the charge of wood chips or 'thelike) and for the feeding in of steam. In the hitherto known types of apparatus of this description, the digester is evacuated either by means of vapors or by means of an air pump or mechanical blower, and that before admission of the boiling lye and after the digester has been firmly closed down, or by letting out a portion of the lye after the filling and closing down of the container. When direct heating of the contents of the digester is adopted, the steam is fed in through one or more perforated pipe coils. When indirect heating of the contents of the digester is adopted, either tubes of acid-proof material are built into the interior of the digester, in which tubes the 'steam is condensed and rendered available for other purposes, without diluting the digesting lye, or preheaters, likewise of acidproof material, are provided outside the digester. If it should be necessary, v in consequence of tight packing of the charge of chips, to circulate the lye for the purpose of heating the same to a uniformtemperature and of preventing the formation of cold pockets, there is usually employed a mechanical pump which must .of course be made of acid-proof material, and which can be disposed either inside or outside the digester. \In the former case the pipes required to carry the lye can also be provided in the interior of the digester. The lye can either be withdrawn from the digester at the top and returned under pressure at the bottom, or vice versa. The direction of ow can also be made to alternate.

The present invention isconcerned with a ce1- lulose digester equipped with means for evacuating the container before commencement of the boiling, for feeding in the lye, for circulating the liquor, and for discharging the contents and/or introducing the Washing water, as also for feeding in the steam; the essential feature of the invention being that for effecting all the feeding, evacuating, and circulating required there are employed exclusively steamor gas-jet devices disposed outside the digester proper, suitably grouped, and connected to the digester by means of appropriate controllable valve members dis posed outside the digester. The jet device employed for evacuation is independent of those tainer after the introduction of the charge.

serving for circulating and heating. By this arrangement of the jet devices for circulating and heating in a convenient position at the operatives stand, the work of tending and controlling the entire boiling process is very greatly facilitated.A 5 At the same time the replacement of the powerconsuming circulating pump by this more suitable and simpler fluid-jet impelling device enables the energy contained in the steam supply to be made use of for effecting circulation of the lye.

The evacuation of the digester and of the chips or other matter constituting the charge results in uniform and immediate penetration of the lye into the material of the charge, and consequently in uniform and undelayed dissolving 'of the en- 15 crusting matter and/or uniform decomposition ofthe Wood, and therefore also in improved strength land whiteness of the cellulose obtained, and in the obtaining of higher yields which means greater economy in the consumption of the start- 20.

ing material used.

'Ihe lay-out of `the plant is extremely compact, since one and the same set of apparatus can be used for a plurality of operations in the course of thel digesting process. Furthermore, no rotating parts are' used, and the wear involved therein is consequently avoided.

A formof construction embodying the invention is shown, by way of example, in the accompanying drawing in which Fig. 1 shows a digester 30 in accordance with the invention in longitudinal section, while Fig. 2 shows a detail of the same.

In the drawing, I denotes the digester which is provided at the top with a feed pipe connection 2 for the introduction of the charge and at the 35 bottom with a discharge pipe connection 3. The usual gas escape pipe 4, which branches olf the feed pipe connection 2, is also connected, with the interposition of a stop-cock 5, to a steam-jet exhauster 5B to which steam is fed through the 40 pipe 5b, for the purpose of evacuating the conthe outside of the digester there are provided further steam jet devices in the form of injectors 6, 1, and 8 which are connected on the one hand, 45 through valves 6a, 1a, 8a, by branches, to a common'steam supply pipe 9, and on the other hand through valves V1, V2, V3 and branches to a pipe cross Ill. From this cross I0 pipes Ila and IIb branch oli, through valves I2a and I2b, to the lye 50 container and tothe Water tank, respectively,

L While a pipe line I3 leads to a perforated tubular ring I4 disposed in the upper part of the digester. The down-pipes from the steam jet devices 6, 1, and 8 merge at I5 intofa common pipe I6 which 55 constituting the charge;

either discharges with its full bore into the lower part of the digester or is branched to two connections II and I8 communicating with perforated tubular rings I9 and 20 disposed in the lower Vpart of the digester I, a pipe 22 being also branched off and discharging intoA the bottom of the discharge connection 3. The usual lye outlet is provided at 2| in the pipe I6.

The mode of operation of the apparatus according to the invention is as follows:-

'I'he digester is rst charged up to the rim with the `material to be digested. After the closing of the upper man-hole 2 and of all other apertures and valves associated with the entire digester, the container is evacuated by means of the steam jet exhauster 5a, with the resulty that the air contained in the pores of the charge escapes, and the lye introduced in the succeeding phase of the procedure can penetrate right into the interior of the shreds or other material On opening the valve I2a, valves V1, V2, V3, and steam valves 6a, 1a, 8a, the lye is introduced and at the same time heated by means of the steam jet injectors 6, 1, and 8. When the digester has been filled with lye, which can be effected 'to a lower level than is otherwise usual on account of the preceding evacuation, the process of boiling is commenced.

Duringthe boiling the lye is turned over or circulated in the digester. To this end, the lye is withdrawn from the top of the container through the perforated tubular ring I4 lby means of the same steam jet devices 6, lI, and 8 as are employed for feeding in the lye, and returned' to the digester at the bottom through the perforated tubes I9 and 20 and pipe 22. At the same time the work performed in circulating the liquor can be regulated by turning on or off one or more of the steam jet devices constituting the set. During the circulating operation the valves I2a and IZb in the pipe lines IIa and IIb are closed. To prevent excess pressure, the mixture of the gas generated in boiling, with liquid and vapour is drawn off, in the usual manner, from thetop of the digester through the pipe 4 and returned to the lye containers, although this venting can be postponed' to a later time than is otherwise usualwhich the lye is removed by opening of the valver 2|. Washing water isthen forced into the botztom of the digester by opening the valve |211, the

three valves 6a, 1a, 8a, and the steam jet devices 6, l, and 8, whereupon the outlet 3 at the bottom of the container -is opened and the digester emptied, accelerated and thorough emptying as also scouring being thereby ensured.

I claim:

1. Apparatus for the preparation of cellulose comprising a boiler, a closure extension at the top of the boiler, a steam jet impelling device connected by a pipe line to the upper part of the boiler and by a further pipe line to the lower part of the boiler and' by a third pipe line to a steam generator, control valves in the said pipe lines adapted to permit, selectively, of the feeding of steam to the boiler, feeding of lye into the boiler, and circulation of the contents of the boiler by removal from the upper part and returning under pressure into the lower part of the boiler, and a. steam jet exhauster connected to the said closure extension for the purpose of evacuating the boiler before commencement of boiling.

2. Apparatus for the preparation of cellulose comprising a boiler, a closure extension at the top of the boiler, a p1ur1ity of steam je@ 1mpelling devices connected to a common pipe line communicating with the upper part of the boiler and to a further common pipe line communicating with the lower part of the boiler; and connected by a third pipe line to a steam generator, control valves in the said pipe lines adapted to permit, selectively, of the feeding of steam to the boiler, introduction of lye into the boiler,

and circulation of the contents of the boiler by removal from the upper part and returning under pressure into the lower part of the boiler, Aand a steam jet ,exhauster connected to the said closure extension for the purpose of evacuating the boiler before commencement of boiling.

3. Apparatus for the preparation of cellulose comprising a boiler, a closure extension at the top of the.boiler, a plurality of steam jet impelling devices ,adapted to be shut oi and turned on independently and selectively and combined to form a unit, the said unit being connected to a common pipe line communicating with the upper part of the boiler and to a further common pipe line communicating with the lower part of the boiler, and being connected by a third pipe line to a steam generator, control valves in the said pipe lines adapted to permit, selectively, of the feeding of ,steam into the boiler,

introduction of lye into the boiler, and circu- Vlation of the contents of the boiler by removal from the upper part and returning under pressurevinto the lower part of the boiler, and a steam jet exhauster connected to the said closure extension for the purpose of evacuating the boiler before commencement of boiling.

4. Apparatus for the preparation of cellulose comprising a boiler, a. closure extension at the top `of the boiler, a perforated tubular ring disposed in the interior of the boiler, a second tubular ring with .outlet apertures disposed in the lower part of the boiler, a plurality of independently and selectively controllable steam .iet impelling devices combined to form a unit, the said unit being connected to a common pipe line communicating with the said first tubular ring and to a further common pipe line communicating with the said second tubular ring, and by a third pipe line to a steam generator, control valves inthe said pipe lines adapted to permit, selectively, of the feeding of steam to the boiler, introduction of lye into the boiler, and circulation of the contents of theboiler by 4removal from the upper part and returning under pressure into the lower part of the boiler, and a steam jet exhauster connected to the said closure extension for the purpose of evacuating the boiler before commencement of boiling.

FRIEDRICH WILHELM LUDWIG SCHEDE. 

